In general, natural gas is transported through gas pipelines of the land or sea in the form of gas, or is stored in an LNG carrier in the form of LNG (Liquefied Natural Gas, hereinafter, referred to as “LNG”) to transport the stored LNG to required facilities in faraway places. Such LNG is obtained by cooling natural gas at an extremely low temperature of approximately −163 degrees Celsius, thereby being decreased to the extent of about 1/600 in volume compared to natural gas in the form of gas. Accordingly, LNG is very suitable for long-distance marine transport. The LNG carrier has an LNG storage tank which is able to withstand extremely low temperatures in order to load LNG and unload the LNG into required facilities on land after sailing the sea.
The following description will be given of a structure of an LNG storage tank in an LNG carrier in accordance with the prior art with reference to the accompanying drawings.
FIG. 1 is a sectional view illustrating an LNG carrier in accordance with the prior art. As shown in FIG. 1, a LNG carrier 1 of the prior art is provided with an LNG storage tank 2 therein. The LNG storage tank 2 is made of a structure and a material which are able to withstand extremely low temperatures, and is equipped with pipes and pumps, which are not shown, so as to supply and discharge LNG.
Such a conventional LNG carrier 1 stores LNG in the LNG storage tank 2 and then transports the LNG to required facilities on land.
Meanwhile, recently, ships utilizing LNG as fuel have been gradually increasing together with an increase in world oil prices. However, since LNG stations for such ships are limited to the land around harbors adjacent to several sea regions, the refueling of the ships is impossible during sailing. For this reason, the ships should move to the harbors for LNG refueling, thereby having time and space restraints.
Currently, ships or floating structures for solving these restraints have not been developed. Since the conventional LNG carrier 1 has only a function to simply transport LNG without an LNG refueling function, there is a problem in that, even in the case of being required to refuel the LNG carrier with LNG on the sea, it may not be solved. This is disclosed in, for example, U.S. Pat. No. 6,805,598 entitled “LIQUID NATURAL GAS TRANSFER STATION”, issued on Oct. 19, 2004.